Hello readers! While I do not make New Year's resolutions, I am making it a goal to update my ChemEd X blog on a more regular basis using video as my medium. In the video below, I will walk you through a kinetics experiment we use in our Chemistry 2 (and Honors Chemistry 2) courses. The lab is called Disappearing X. Please feel free to comment below with any thoughts or questions you may have. The pdf documents for the lab handout and lab report templates are attached below.
During our stoichiometry unit, I wanted my students to take part in an engaging investigation. Many of the stoichiometry labs I had done in the past followed more of a traditional structure involving something like, “here is the reaction…predict how much…do the reaction…compare to prediction…determine % yield.” While merit for such a lab can be argued for, I really wanted to immerse my students in an actual investigation that more accurately reflected the scientific skills I try to advocate for—experimental design, data collection, analysis, creating an argument from evidence, engaging in argument, etc. To achieve this, I opened my Argument-Driven Inquiry in Chemistry (ADI) book and happened to find a wonderful example.
Though I had used a version of the decomposition of sodium bicarbonate lab in our stoichiometry unit for years, with consistent results, what the ADI book provided was a surprisingly different and more creative approach.
The students are provided with four different balanced chemical equations that could explain how the atoms are rearranged during this decomposition.
Option 1: NaHCO3 (s) à NaOH (s) + CO2 (g)
Option 2: 2NaHCO3 à Na2CO3 (s) + CO2 (g) + H2O (g)
Option 3: 2NaHCO3 (s) à Na2O (s) + 2CO2 (g) + H2O (g)
Option 4: NaHCO3 (s) à NaH (s) + CO (g) + O2 (g)
Their task: Figure out which balanced chemical equation accurately represents the decomposition of sodium bicarbonate.
At first glance, the ingenuity of this challenge was not completely obvious to me. As chemistry teachers, the depth of our content knowledge allows us to systematically rule out three of the reactions without even performing the experiment. Even if we did need to do the investigation ourselves to determine the right equation, our experience in the lab and overall scientific literacy allows us to easily come up with a plan and identify exactly what we should be looking for.
However, our students are novices. They lack the content knowledge and they most certainly lack the laboratory skills to easily generate a plan for arriving at an evidence-based answer. While they might be lacking in these areas, they are not completely clueless. They know just enough to successfully accomplish their task, even if they do not immediately start making connections to content already learned. At the same time, their lack of knowledge prevents them from confidently knowing the correct reaction prior to investigation.
After thinking about it a bit, there were at least five distinct features that convinced me to pursue this lab.
We had just finished our reactions unit, so they were all familiar with the generalized pattern that a decomposition reaction follows.
To the students, this reactant is a complete curveball. As novices, they have no idea how to confidently predict the products of such a reaction. You know their gut instinct will be to suggest it decomposes into sodium and bicarbonate. As absurd as this seems to you and me, it seems plausible to many of them. Even though I could have given them a brief explanation as to why something like this would not decompose in this manner, I did not need to since it is not even offered as a potential equation—away with bicarbonate!
Since we were nearing the end of our stoichiometry unit, this was a perfect application. Though some of the products can be easily determined qualitatively, stoichiometry will need to be applied when trying to identify the solid product that remains. The use of stoichiometry to generate sufficient evidence that will support their eventual conclusion will be the meat of their argument.
During our reactions unit, they had learned about testing for certain gases using a flame test. Because of this, many of them remembered that they could identify the presence of CO2 and O2 based on what happened when a lit splint was placed into the test tube.
Sometimes it is hard to reduce, let alone eliminate, previous conceptions and biases when asking students to develop an argument from evidence. However, since each reaction appears equally plausible from the perspective of the student, this meant the evidence gathered was the primary driver behind the construction of their argument. They could not rely on prior knowledge alone simply because they lacked sufficient prior knowledge that would allow them to know what the products should be without even performing the investigation.
Though I demonstrated some basic safety tips, how to set up their apparatus, and the general approach to performing the reaction, the bulk of the experimental design was going to be on them. For the first time, they actually needed to consider questions such as:
Figure 1- Example questions from the ADI book
With respect to materials, I gave them the following list of equipment and the chemical they were going to consume.
Consumable: Solid NaHCO3
Equipment: Bunsen burner, lighter, test tube, glass stir rod, tongs, electronic balance, periodic table
When they were finished, each group was required to produce a whiteboard that resembled the following structure:
Figure 2 - Whiteboard Template
While the method used for groups to communicate their argument to others can easily vary from teacher to teacher, I decided to have 2-3 groups come together and present their findings to each other. It was exciting listening to their conversations that would sometimes lead to genuine discourse, as opposed to a one-way presentation of results. As a teacher, my favorite scenario was when different groups would have different conclusions and, consequently, different chemical reactions proposed. Hearing them use their knowledge of stoichiometry to justify why their results made sense or pointing out the faulty reasoning in another group’s results was something I wish I had recorded.
I had mentioned that one of the characteristics I liked about this lab was the student involvement in experimental design. Even though this feature is a hallmark trait of every ADI-themed lab, it was still a relatively new experience for me. Each group was given approximately 20 minutes to come up with an outline for their experimental design. While I had previously shown them how to safely perform the reaction, I gave them no guidance on what data to collect or even how to collect it. I did not tell them how long to heat their sample or what to look for when determining if the reaction is complete. This really threw them off and I could sense the frustration from several groups because, for once, I was not spoon feeding them every single detail of each step in the procedure.
By letting them take ownership of their experimental design, a few things happened to some groups that served as a learning experience and opportunity for discussing the importance of experimental design within the scientific process.
1. Some groups simply did not heat their sample for a long enough time. Doing so resulted in a much higher product mass than they had predicted since there was still unreacted sodium bicarbonate in the test tube. When trying to explain how their percent yield was over 100%, several groups initially struggled to realize they had just simply stopped the reaction too soon. This made for good conversation regarding experimental error.
2. I was truly amazed by how many groups did not take the time to think about how they were going to collect their mass data. Everyone knew they needed the mass before and after, but several groups never considered exactly how they were going to do this. Some groups only recorded the mass of their sodium bicarbonate, without considering the mass of their test tube and glass stir rod. Doing so meant that, when their reaction was complete, they were going to empty the contents of their test tube into a plastic weighing container to collect the final mass. What they did not consider was that the contents of their test tube were going to still be really hot. So, when they transferred their product to the container that was on the scale, their product literally melted right through the container! (See below) Now there was product all over the scale and on the table. Groups that did this immediately recognized the flaw in their experimental design and I honestly saw it as a wonderful learning opportunity.
Figure 3 - Hot samples melt plastic.
3. Some groups literally filled half of their test tube with sodium bicarbonate. Doing so resulted in the reaction seemingly taking forever to complete. In addition, since they started with so much reactant, they never really considered the decrease in probability of successfully using up all their reactant.
While most groups executed the experiment without major flaws, I was reminded of the importance in giving them experiences that provide opportunities for failure and reflection in the lab. Students need to experience the fact that science is not just a linear process driven by knowing exactly what to do and exactly what to expect every step of the way without hiccups. Sometimes our experiments fail or produce results that do not make sense. When this happens, we think about how we can improve the experiment and do it over again. After accounting for our mistakes, if we are still surprised by the results, maybe there is something new to learn about the nature of reality!
Students need to experience the fact that science is not just a linear process driven by knowing exactly what to do and exactly what to expect every step of the way without hiccups.
Overall, the lab itself took anywhere from 20-30 minutes to set up and execute. Students had the remaining 20-30 minutes of class to analyze their results and develop their initial argument; which was going to be finalized and communicated the following day.
Whether you are looking to add a bit more scientific inquiry to your labs or simply looking for a great stoichiometry lab that can be added to your collection, I encourage you to try something like this with your students!
Though you will need to purchase the Argument-Driven Inquiry in Chemistry book to access the full teacher handout and notes, you can find a free student-version lab handout online. I also included it in the Supporting Information below.
Editor's Note: Readers may be interested in reading a Pick about Argument-Driven Inquiry in Chemistry posted Chad Bridle.
1Argument-Driven Inquiry in Chemistry. Stoichiometry and Chemical Reactions: Which Balanced Chemical Equation Best Represents the Thermal Decomposition of Sodium Bicarbonate? NSTA Press, 2015, pp. 426 – 441.
Like many schools, this year my school went 1:1. Each of our students was issued an 11 inch Chromebook with a webcam. Our upperclassmen have the the older Samsung models with a front-facing webcam and our underclassmen have the new Lenovo N22/23 models with a flippable webcam. I am a “jump in head first” type of person so I decided to go completely paperless this year. I figured the worst thing that could happen is I would go back to paper. Now that I am halfway through the year (and still paperless!), I wanted to share what has been working well for me and where the snags have been.
Last year I compiled packets for all of my units to replace composition books and single worksheets. This allowed me to scaffold good lab note organization and helped students organize their thoughts and papers. That made it easy to transition to paperless because I already had all of my resources compiled together.
I played around with a few different methods for creating editable materials for students and finally settled on Google Slides distributed through Google Classroom. It is a little time consuming to make the digital packets but it is worth it to help my students stayed organized. It is especially helpful for my ninth grade students to have all of their worksheets and notes for a unit in one document. To create a digital packet, I convert all of my note pages and worksheets to image files, insert the image into Google Slides as a slide background and then add text boxes where my students need to type. The most time consuming part is adding the text boxes but it really speeds things up for your students if they do not have to do that part. Students add things that are hard to type (like drawings) to their digital packets by drawing them on a small dry erase board (a piece of graph paper in a page protector) and inserting a picture from their webcam. My students still take assessments on paper.
Here is what one of my lab pages might look like:
Figure 1- Example Lab Page
I color code sections for my 9th grade students so they know which part is for their own ideas and observations (white), which part is practice (green) and which part is the take away point we come up with as a class (blue). My 9th grade classes are co-taught so my co-teacher will type notes on the SMARTboard during the class discussion as a visual cue for students.
There have been far more positives than negatives in this endeavor. The transition to paperless has been most beneficial for my 9th grade students for a few reasons:
The biggest struggles in the transition to a paperless classroom have resulted from students needing to document their work on whiteboards and then take a picture of it. I have had three main issues:
I honestly did not know how going paperless would work out when I started this and I was fully prepared to fall back on my traditional paper packets. Overall, I think there are more pros than cons. I have certainly loved not spending time at the copy machine!
Is your school 1:1? How have you leveraged the technology in your chemistry classroom?
Where do students do most of their learning about science? In the classroom? I got a surprise only two sentences into my reading of Characterizing the Landscape: Collegiate Organizations’ Chemistry Outreach Practices by Pratt and Yezierski (available to all readers as an ACS Editors’ Choice article). The surprise: “…only 18.5% of K–12 learning occurs inside the formal classroom with the rest of learning occurring in informal environments.” The authors list some of these environments, such as gaming, TV, internet, museums, and afterschool clubs. This introduction pulled me into the rest of the article, with its focus on chemistry outreach done by college students and faculty during demonstration shows and hands-on activities with K–12 students and the public.
Between American Chemical Society (ACS) student chapters and Alpha Chi Sigma collegiate chapters, this type of outreach has the potential to touch nearly a million audience members or direct participants. Pratt and Yezierski surveyed college students and faculty members from these two organizations, investigating 1) the purpose of the outreach, 2) commonly used activities, and 3) any methods used to evaluate the outreach.
Figure 1 - Characterizing the Landscape: Collegiate Organization's Chemistry Outreach Practices preview image
It was the third area that most piqued my interest. The authors begin their discussion of it with the statement: “Data related to the evaluation of outreach events were shallower than anticipated by investigators.” They also discussed challenges involved with evaluation. The method most mentioned in the survey was to simply observe the audience. One response was, “I just look to the faces of our guests to see if they are enjoying themselves.”
My local ACS High School ChemClub has hosted hands-on Summer Science at the Farmers’ Market using ChemClub community activities grants. I had not deeply considered how to evaluate whether it was a success and worth the time, energy, and money it took. More effort was definitely put into planning, practicing, and carrying out the activities than evaluating their impact on visitors. I was able to tally how many adults and children stopped by the booth to participate in each activity and made note of how many participants came back to do more of our activities later in the season. One-on-one conversations with visitors gave clues as to their enjoyment and learning. But had it really achieved its main goal of helping participants to realize how chemistry connects to their everyday world? In the article, Pratt and Yezierski suggest further research of connections between the goals set for various informal science education events and evaluation of the events.
Although the current paper focused on the college level, I know there are high school educators using demonstration shows and hands-on activities for outreach. What have you done? How have you evaluated your outreach?
Mary Saecker’s post JCE 95.01 January 2018 Issue Highlights breaks down the issue for you, including a closer look at the microscale demonstration shown on the cover. She has also combed the JCE archives for articles about the three outreach activities most mentioned in Pratt and Yezierski’s article discussed above: liquid nitrogen ice cream, elephant toothpaste, and slime.
Might your 2018 plans have space for sharing your thoughts with the XChange community? We’d love to hear your take on past JCE articles and how you have used them in your classroom. Start by submitting a contribution form, explaining you’d like to contribute to the Especially JCE column. Then, put your thoughts together in a blog post. Questions? Contact us using the ChemEd X contact form.
"What are we doing to help kids achieve?"
My students just finished an activity about isotopes. Each year there is always one or more student who ask about the mass of isotopes. How do scientists solve for that mass experimentally?
One way scientists do this is by using a mass spectrometer. Mass spectrometers first form atoms into ions and then pass them through magnetic fields. Atoms of different masses respond differently to the magnetic field. Flinn Scientific has a nice model of this. It is simply a piece of plexiglass with a magnet underneath. The "atoms" are metal spheres rolled down a ramp. The magnet effects the spheres differently based on their masses. I have used this model but with a twist suggested by Irwin Talesnick. Irwin does a similar experiment but with one added feature. The plexiglass is coated with paper and the students do not know the magnet is present. They must predict what will happen. The first "atom" is a large billard ball and it goes straight.The next "atom" is as large as the billiard ball but is metallic, which represents the "ion" idea. Subsequent "isotopes" are deflected more or less based on their mass. This is similar to an actual mass spectrometer. Students usually have an "aha" moment when the second "atom" is deflected and then they quickly want to look underneath the plexiglass.
Mass Spectrometer Model
I have been doing this for several years. It always seems to get a nice reaction from students. They want to explore the idea more and it generates questions. It also costs much less than an actual spectrometer.....
Do you have a great quick demonstration? Would love to see it...don't be afraid to share...
Displacement reactions are an essential way to demonstrate the reactivity series of metals. I have tried many different methods to demonstrate or perform displacement reactions over the years with mixed results regarding one particular metal, aluminium. Based upon my experience, the behavior of aluminium in displacement reactions often confuses students. In light of this, I have introduced a trick involving aluminium displacement reactions that hopefully helps students understand and remember (‘stick in their mind’ so to speak) these reactions.
To carry out the reaction, a small aluminium boat is constructed from a square piece of foil (about 5 cm2). Dry copper nitrate powder (about 1 g, quantities don’t need to be exact) is added on top. A few drops (approx. 5 or 6) of water is then dripped from a plastic pipette in order to wet the powder. No reaction is observed, even after waiting one or two minutes (Figure 1, left). The experiment is repeated using copper chloride instead of copper nitrate. Almost immediately, the aluminium foil breaks apart, releasing a gas (fizzing) and water vapor into the air (Figure 2, center)! The reaction is very exothermic and sudden. A red/brownish ppt. (copper metal) is left behind:1
silver green-blue colorless red/brown
The fizzing is due to the formation of hydrogen gas in the reaction between the aluminium foil with hydrogen ions present in solution:1
For the trick, another piece of foil is produced but in this case tin foil (which looks very similar to aluminium foil) is used. Before carrying out the trick, I pose a few questions: Why does the copper nitrate not react? Was it the aluminium foil? Was it that a different copper salt was used? To address the questions, the copper nitrate experiment is repeated (this time with the tin foil, however) and sure enough an exothermic reaction ensues within a few seconds (Figure 1, right). So much heat is generated that the nitrate might decompose releasing brown toxic nitrogen dioxide gas and it can even catch fire if the boat shape is rolled into a cigar shape.
silver blue colorless red/brown
In addition, hydrogen gas is evolved as before, presumably due to the reaction between tin and protons:
Figure 1 - Aluminum foil with copper II nitrate solution (left) and with
copper II chloride solution (center). Tin foil reacting with copper II nitrate solution (right).
By now, I have many perplexed faces staring at me. I then reveal ‘the trick’: I reacted tin with the copper nitrate, not aluminium! After disclosing this to the students, the real detective work begins. I explain to the students that aluminium metal has an outer layer of very unreactive aluminium oxide,2 while tin does not have such a layer. The oxide layer in aluminium must be penetrated in order for the aluminium metal to react.2 Chloride ions (bromide ions work, too) act as a catalyst that allows the aluminium oxide layer to be penetrated, allowing the reaction with copper ion to occur.
The video below displays the effect of adding water to a mixture of Cu(NO3)2 (s) with Al(s), CuCl2 (s) with Al(s), and Cu(NO3)2 with Sn(s).
The case of aluminium metal in single replacement redox reactions video from ChemEd Xchange on Vimeo.*
* The formula for copper II nitrate under the reaction on the right should read Cu(NO3)2.
1. Flinn Scientific ChemFax, Foiled Again: Aluminum Loses to Copper, 2017.
2. Flinn Scientific ChemFax, Foiled Again: Single Replacement Reactions, 2016.
The American Association of Chemistry Teachers (AACT) has just made a major announcement. The first AACT Chemistry Teacher of the Year Awards have just opened their nomination process. Awards will be given to teachers in each of three levels of chemistry education. One for K-5 teachers of science, one for grade 6-8 teachers of physical science, and one for high school chemistry teachers.
The application criteria seems pretty straight forward. It is an online application that does require a few short essays including “In what ways have you contributed to AACT”, “How has your involvement with AACT impacted your students”, “How has your involvement with AACT impacted your colleagues” “How has your involvement with AACT impacted you as a professional educator”. There is some brief biographical information required and one letter of support from a non-family member. Applicants must be members of AACT and will receive a $1000 cash prize and one year of membership in AACT. Applications close on February 28.
As I read through this, and I only heard about it myself yesterday, I recognize that this is not just about teaching kids but also about teaching teachers. I have prided myself on being a role model for other teachers and providing a lot of professional development opportunities for my colleagues here in the Los Angeles area and nationally. To see that us “Teachers of Teachers”, as I described myself on my Twitter feed, are going to be recognized makes me very happy. I love everything I do with my high school students but I am also very fond of what I have taught to other teachers. I think it is important for applicants to mention how they have supported their own colleagues.
I am really excited to see that AACT is also including K-8 teachers in this. There is so much we can accomplish in exciting younger students. We should absolutely put a heavy emphasis on improving their exposure to chemistry.
For more details, read the announcement on the AACT website.
For better or worse, I've seen very little of Richard Feynman's work/videos/lectures/etc. But a while ago, somewhere in my Twitter Timeline, somebody mentioned a transcription of a Richard Feynman interview about magnets. Since I don't actually teach much about magnetism in my chemistry courses, I almost skipped right on past the link. But instead, I took a couple minutes to check out the transcription of the interview - and then watched the video embedded below.
I realized I'd been missing out on a gem. Now, I can't wait to find more time to watch Richard Feynman interviews. Call me sentimental, but the big highback chair and the glasses case and pens in the shirt pocket remind me of my dad! But I digress. Sorry.
This video was originally posted on the nebulajr YouTube channel April 15, 2009.
I would like to share how I used this blog-post transcription and video with my IB Chemistry students. First, without much prompting about the discussion, I simply gave my students a printed copy of the transcript and then showed them the video. (Note: Some of my students preferred to only listen, while others followed the interview through the written text, thus making it more accessible to them. That's my main reason I chose to provide a written copy.) I didn't pause the video or offer any interruptions or commentary. I simply let the students watch the interview. Then I had them work in their groups on the questions listed below. Each question was followed up with discussion.
A bit of discussion followed their table group chat. With three classes discussing this video over about a two-week period due to scheduling issues, I don't remember many of the details, but I do recall students getting into the idea of how truly deep you can go when explaining something. One student said that each "Why?" leads to another level of depth - and another "Why?". And so on, until you either get to the heart of the matter, or your understanding finds exceeds your limit.
Again, the details are murky - but the students weren't bothered by the lack of chemistry content in the video. Rather, they brought forth ideas we'd been discussing - such as hybridization of orbitals and how that can be a model to explain molecular shapes.
I always enjoy this type of question for almost any reading, as it is so open-ended and groups of students rarely offer the same choice. I had a PDF of the transcript on my screen and ended up with highlighted text from all over after each of the five groups. Sometimes with a discussion like this I end up asking other groups to evaluate a choice, stating whether they agree or disagree with the importance of the sentence and the reasoning given by the original group. Of course, time can be a factor here, but there's no doubt I enjoy the discussions.
So what do I hope students get out of an activity like this? I won't claim it's "real chemistry" per se. It certainly isn't to raise IB test scores. Rather, it's to engage them in discussion about bigger issues - like what the question "why?" really means in science - compared to "how?"
And I'll even admit an ulterior motive here: I want the students to understand how even a Nobel-winning physicist can admit that "why?" isn't always easy to answer - for reasons I'm certain the students hadn't considered before. I felt a sense of relief when I read the transcript for the first time, thinking even more than ever that it's OK if I can't answer EVERY "Why?" that is thrown my way. I also like students to see that analogies have limitations. From Dr. Feynman, "I can't explain that attraction in terms of anything else that's familiar to you. For example, if we said the magnets attract like if rubber bands, I would be cheating you. Because they're not connected by rubber bands. I'd soon be in trouble. And secondly, if you were curious enough, you'd ask me why rubber bands tend to pull back together again, and I would end up explaining that in terms of electrical forces, which are the very things that I'm trying to use the rubber bands to explain." I'll admit that I like to use analogies - but lately I've tried to move away from them and focus more on the model we are discussing, and accepting that each model (E.g. VSEPR, hybridization, MO theory) has advantages and limitations.
Since I teach IB courses, the connection to the Nature of Science and Theory of Knowledge is helpful as well. In summary, each science course in the IB is tasked with exposing students to the true nature of science (well, as defined by the IB, I suppose). Essentially, that science is a way of thinking more than it is a body of knowledge. And that there are many connections between science and our history and society. Theory of Knowledge is a course students take that discusses the very essential question, "How do we know what we know?" Any discussion I can use to get students thinking about this question - and knowledge in general - I view as a positive.
Do you have any favorite videos or articles that are not directly chemistry, but rather on the nature of science or related topics?
What did you think of the interview? Is it something you would share with your students?
For a few years now, I have been using a simple laboratory experiment that allows students to calculate the wavelength of various colors of light. I use the activity near the beginning of the semester, when students are first learning about measurement, unit conversions, and significant figures. If you would like to skip reading through the details, scroll down a bit and you will find a video that demonstrates the experimental details and associated data analysis.
The experiment is based on the diffraction of LED light through a diffraction grating. I use rainbow glasses for the diffraction grating. When light passes through a diffraction grating, some of it gets “bent” from its straight line path (Figure 1):
Figure 1 - Light from a red LED (circle on left) passes through a diffraction grating (rainbow glasses). The distance between the light source and diffraction grating is designated L.
Notice that we can extend the diffracted beams of light back towards the light source (Figure 2), such that the distance y is the distance between the light source and the image of its next nearest neighbor as viewed through the diffraction grating:
Figure 2 - The double blue arrow represents the distance between the light source and its next nearest neighbor as viewed through the diffraction grating. This distance is designated y.
The following relationship exists between the wavelength of light emitted, l, the distance between the slits in the diffraction grating, d, y, and L (see Note 2 for derivation of Equation 1):
This experiment generally yields good results. In fact, if students report results that aren’t within 10% of the appropriate wavelength I know something has gone wrong. Occasionally careless measurement is the culprit. However, it is most often mistakes in unit conversion that gets in the way. I give students the value of d = 4.85 x 10-4 cm, and then have them report to me the wavelength of light in nm. Doing this serves the purpose of requiring students to correctly use scientific notation and conversion of metric units (cm to nm) to obtain reasonable results. I also note that students will often measure L in meters and y in centimeters – but not convert to consistent units when using Equation 1. This of course leads to spurious results but allows for a teaching opportunity on the importance of paying attention to units. And there is always the student who measures y in inches and L in meters but doesn’t write down units.
The video below provides a demonstration on how to carry out this experiment and analyze the data.
1. Using the distance between the slits (d) in the diffraction grating as recorded by the manufacturer of the glasses has caused me some trouble in this experiment. The rainbow glasses I use in this experiment are listed as having 500 lines per mm, which would imply d = 2000 nm (1 mm /500 lines = 0.002 mm; see why this is a great lab for unit conversions?). However, I have used an optical microscope fitted with a length scale to measure d = 4850 nm in the glasses I use. The moral of this story is if you notice that your measured wavelengths don’t make sense (200 nm for red light, for example), then consider measuring d for yourself. If you don’t have an optical microscope fitted with a length scale, then simply conduct this experiment with light of known wavelength and use the following equation to determine d:
2. The bending, or diffraction of light through the diffraction grating is given by:
Where l is the wavelength of light, d is the distance between slits in the diffraction grating, and q is the angle between the straight-line beam of light and its next nearest neighbor. Notice that we can extend the diffracted beams of light back toward the light source (Figure 1). Upon doing so, we produce a triangle with hypotenuse, h, and the new angles produced are also equal to q (Figure 3).
Figure 3 - Extension of diffracted light beams back through space to the light source. The angle between the straight-line beam and diffracted beams is q. The hypotenuse of the triangle formed is designated h. The double blue arrow represents the distance between the light source and its next nearest neighbor. This distance is designated y.
We can substitute sinq = y/h into Equation 2:
By using h2 = L2 + y2, we obtain the equation we seek:
A student laboratory sheet is included in the supporting information below.
I have a confession to make: I’m a mean teacher. I make my junior chemistry students learn the element names and symbols--all one hundred and eighteen of them.
You might say that’s impossible, a waste of time, or downright unnecessary in today’s age of information at your fingertips. When I was a new teacher, I might have agreed. I started my first year teaching in November following a long term sub who had covered atomic structure and bonding--you know, the fundamentals.I decided we could get right to chemical nomenclature and then writing and balancing chemical equations. You can probably guess how that worked out, since I’m writing this.
I soon realized that asking my students to write and interpret chemical formulas without knowing the symbols for the elements was akin to asking someone to spell words and write sentences without knowing the alphabet. Over the past few years I have tried numerous tactics from making flashcards to having quizzes over progressively larger chunks of elements. Early on I considered choosing only certain elements that needed to be memorized but soon decided that any list I would choose would be arbitrary at best and leave my students unexposed to vast swaths of the periodic table. I certainly didn’t want MY students mistaking dilithium, vibranium or unobtanioum for real elements!
Those first few years, I had significant resistance from students to learning all the elements. However, once I proved that it could be done (I flexed my geeky bravado and recited all the elements from memory) they came around to the idea as a challenge worth accepting. My students still find chemical nomenclature and writing and balancing chemical equations challenging, but at least they know their alphabet first. Here are a few of the methods (in no particular order) I have found useful.
It may sound simple, but one of the assignments I give the first week of school is to make a set of flashcards by hand. Even though there is an "app for that" as at least one student reminds me every year, the physical act of making the cards has immense value. I ask students to bring these cards with them to class regularly and as a filler activity will ask them to pull out their flashcards and quiz their lab partner.
Figure 1 - Element Flash Cards
How do you eat an elephant? One bite at a time. Inspired by this old joke, and my theology teacher next door neighbor who had students learn scripture memory verses, I broke the periodic table into chunks of 10-ish elements. Every two weeks, students are quizzed over the next ten elements plus a few elements from earlier on in the year chosen at random. Following this schedule, students know the vast majority of the elements by the first part of second semester in time to write chemical names and formulas. You can find some sample quizzes in the supporting information below. (Note: I have not updated these quizzes to include the most recent four elements since I am using Sporcle to create my quizzes now.)
Figure 2 - Sample Element Quiz
Having fun is one of the best ways to learn, and my students actually like playing this game. You can find an explanation of the game here from the Huffington Post. You can use any version of the periodic table you like to make the game--I favor one with just the symbols. This is a great filler activity if you have an awkward 15-20 minutes, say before an assembly or early dismissal. I have included a periodic table for your use in the supporting information below.
Spelling bees are a staple of elementary school, though less commonly in high school. I frequently do an “element bee” with my classes, and while I don’t usually do spelling of the names with this game, of course you could play it that way. Everyone stands up and using my own set of element flash cards I give the first student an element name or symbol. If I give the symbol, they have to give the name, and vice versa. Again, this is a good filler activity, for like 5 minutes at the end of class.
Working in a PS-12 school (under one roof), I have an unusual opportunity to glean ideas from my colleagues from a variety of subject areas and grade levels. I picked this idea up from my colleague who teaches fifth grade. To play this game (chemistry style) you have the students stand in a circle. The first student is given the name of an element. They have to give the first letter and as the students go around the circle each gives the next letter. If they get the letter wrong they are out of the game and must sit down. The game continues around the circle until the element name is complete. The next person after the last letter says the name of the element, the symbol and “cherry pie.” That student is then out and sits down. The next student in the circle starts the next element. I haven’t given really any thought why it is called Cherry Pie...my best guess is that pies are...circular?
Again, inspired by a colleague, (this time our high school social studies teacher), I decided to experiment with using Sporcle as an alternative to cumulative quizzes this year as my school has gone to a one-to-one chromebooks program. This year instead of doing the cumulative quizzes I chose three different sporcle quizzes: element to symbol match, element by symbol, and element abbreviations and scheduled them in rotation once a month. Each month the bar is raised for how many elements are needed to earn full credit. This has been very successful this year!
Sporcle, Inc. . (2007, January 30). In Sporcle. Retrieved from https://www.sporcle.com/
Touch Press Inc. (2018). In The Elements FlashCards. Retrieved from https://itunes.apple.com/us/app/the-elements-flashcards/id835885718?mt=8
Wanshel, E. (2016, October). In Mom Creates Periodic Table Battleship Game To Teach Her Kids Chemistry. Retrieved from https://www.huffingtonpost.com/entry/mom-creates-periodic-table-battleship-game-to-teach-her-kids-chemistry_us_5697f3d4e4b0b4eb759da83b
Mr. Benjamin O'Hearn, JD, Former Teacher of Theology
Mrs. Kaye Sandborn, Teacher of Social Sciences
Mrs. Gayle Thelen, Teacher, 5th Grade
"What are we doing to help kids achieve?"
The concept of the mole has always been a challenging topic for myself and my students. The challenge comes in part when we try to imagine 6.02 x 1023 of anything. Another challenge for some students is the math and theory behind this number and concept.
Years ago I started using and tweaking an activity found in an old version of Zumdahl’s “World of Chemistry” textbook. Students start with four different type of beans. They count 50 of each bean and find the mass of each set. Students use the mass of 50 of the smallest bean and divide all of the other masses by this number. They then get the “relative” masses compared to the smallest bean. Some sample data is shown in Table 1.
Table 1 - Students find the masses and relative masses of sets of 50 beans of four different types.
In the above example, 50 lentils had a mass of 2.43 grams. Fifty white limas had a mass of 14.5 grams. 14.5 grams divided by 2.43 grams is 5.97. This is the “relative” mass of the white limas as compared to the lentils. The relative masses of the other beans were calculated in the same manner. They were all compared to the lentils. Students had just done an activity prior to this in which the examined data that showed that as long as you are comparing the same number of items, you are also comparing the same mass ratios.
Here is where I “tweaked” the published activity. My students were instructed to carefully place on a scale for each bean an amount of beans that would get them to the relative mass for that bean. As an example, they had to place an amount of lentils on the scale to get to one gram. They then had to place white limas on the scale to get to 5.97 grams. They would repeat this for the pintos and black beans. Now the emphasis was on a simple question. Will the number of beans in the end for each relative mass in grams (which by the way was given the unit "a pot") be the same or different for all the beans? You can see some sample data in Table 2.
Table 2 - Finding the number of beans with a mass equal to the relative mass of each type of bean.
In the end, students saw that the same number of beans would provide the same ratio of masses of beans (Table 1). The opposite is also true. The relative mass of the beans in grams would provide the same numbers of beans which is about 20 (Data Table 2). If they did not want to count out a bunch of beans, they could just count by using the relative masses and a scale. This provided a great model for the mole. It took awhile but it was an easy transition from the relative masses of atoms and amu's to molar mass and the mole.
Moles seem to be tough for students and teachers. Do you have a great mole activity? Please share….would love to take a look.
Curricular Alignment for Student Success
The February 2018 issue of the Journal of Chemical Education is now available online to subscribers. Topics featured in this issue include: diversity within the classroom; assessment and curricular alignment; innovations in laboratory curriculum; electrochemistry; analytical chemistry labs; exploring materials science; engaging teaching approaches; historical perspectives; distilling the archives: lab-on-a-chip and microfluidic devices.
Cover: Erasing the Glow in the Dark
Phosphorescence of glow-in-the-dark products is initiated by light with energies that are specific to each phosphor composition. In many cases, the phosphorescence of these materials can also be darkened by further excitation with light that has lower energy than the minimum energy required to produce the initial glow, as demonstrated in Erasing the Glow in the Dark: Controlling the Trap and Release of Electrons in Phosphorescent Materials by William A. Getz, Dannielle A. Wentzel, Max J. Palmer, and Dean J. Campbell and illustrated on the cover: (upper left) shining blue light on paint containing copper-doped zinc sulfide (ZnS:Cu) excites electrons from lower to higher energy levels, as represented by the overlaid stencil; (upper right) the electrons trapped in higher energy levels slowly return to lower energy levels, producing green phosphorescence when the blue light and stencil are removed; (lower left) shining red light on excited ZnS:Cu phosphorescent paint facilitates the electrons returning from higher to lower energy levels, as represented by the overlaid stencil; (lower right) removing the red light and stencil reveals the phosphorescence extinguishing, or the erasing effect. (Photos by William A. Getz.)
Editorial
In the Editorial Hey, Professor—Something Is Wrong in the Book, Norb Pienta discusses how differences among textbooks, electronic books, and content material on the Internet often lead to student confusion and how some of the issues can be resolved by focusing on conceptual understanding with less focus on factual knowledge.
Diversity within the Classroom
Taking Advantage of Diversity within the Classroom ~ Emily V. Goethe and Coray M. Colina
Investigating the Influence of Gender on Student Perceptions of the Clicker in a Small Undergraduate General Chemistry Course ~ Emily D. Niemeyer and Maha Zewail-Foote
Assessment and Curricular Alignment
Adapting Assessment Tasks To Support Three-Dimensional Learning ~ Sonia M. Underwood, Lynmarie A. Posey, Deborah G. Herrington, Justin H. Carmel, and Melanie M. Cooper (available to non-subscribers as part of ACS Editors’ Choice program)
The ACS Exams Institute Undergraduate Chemistry Anchoring Concepts Content Map III: Inorganic Chemistry ~ Keith A. Marek, Jeffery R. Raker, Thomas A. Holme, and Kristen L. Murphy (available to non-subscribers as part of the ACS AuthorChoice program)
The ACS Exams Institute Undergraduate Chemistry Anchoring Concepts Content Map IV: Physical Chemistry ~ Thomas A. Holme, Jessica J. Reed, Jeffrey R. Raker, and Kristen L. Murphy (available to non-subscribers as part of the ACS AuthorChoice program)
Awareness, Analysis, and Action: Curricular Alignment for Student Success in General Chemistry ~ Sarah Jewett, Kathy Sutphin, Tiffany Gierasch, Pauline Hamilton, Kathleen Lilly, Kristine Miller, Donald Newlin, Richard Pires, Maureen Sherer, and William R. LaCourse (available to non-subscribers as part of the ACS AuthorChoice program)
Innovations in Laboratory Curriculum
Effects of Implementing a Hybrid Wet Lab and Online Module Lab Curriculum into a General Chemistry Course: Impacts on Student Performance and Engagement with the Chemistry Triplet ~ Stefan M. Irby, Emily J. Borda, and Justin Haupt
Teaching through Research: Alignment of Core Chemistry Competencies and Skills within a Multidisciplinary Research Framework ~ Eman Ghanem, S. Reid Long, Stacia E. Rodenbusch, Ruth I. Shear, Josh T. Beckham, Kristen Procko, Lauren DePue, Keith J. Stevenson, Jon D. Robertus, Stephen Martin, Bradley Holliday, Richard A. Jones, Eric V. Anslyn, and Sarah L. Simmons
Problem-Based Approach to Teaching Advanced Chemistry Laboratories and Developing Students’ Critical Thinking Skills ~ Joseph G. Quattrucci
Lab-on-a-Chip: Frontier Science in the Classroom ~ Jan Jaap Wietsma, Jan T. van der Veen, Wilfred Buesink, Albert van den Berg, and Mathieu Odijk (available to non-subscribers as part of the ACS AuthorChoice program)
Electrochemistry
A Practical Beginner’s Guide to Cyclic Voltammetry ~ Noémie Elgrishi, Kelley J. Rountree, Brian D. McCarthy, Eric S. Rountree, Thomas T. Eisenhart, and Jillian L. Dempsey (available to non-subscribers as part of ACS Editors’ Choice program)
Reusing a Hard Drive Platter To Demonstrate Electrocatalysts for Hydrogen and Oxygen Evolution Reactions ~ Ricardo H. Gonçalves
Assessing the Electrochemical Behavior of Microcontact-Printed Silver Nanogrids ~ Wesley C. Sanders, Peter Iles, Ron Valcarce, Kyle Salisbury, Glen Johnson, Aubry Lines, John Meyers, Cristofer Page, Myles Vanweerd, and Davies Young
Open-Source Low-Cost Wireless Potentiometric Instrument for pH Determination Experiments ~ Hao Jin, Yiheng Qin, Si Pan, Arif U. Alam, Shurong Dong, Raja Ghosh, and M. Jamal Deen
Analytical Chemistry Labs
Studying Intermolecular Forces with a Dual Gas Chromatography and Boiling Point Investigation ~ William Patrick Cunningham, Ian Xia, Kaitlyn Wickline, Eric Ivan Garcia Huitron, and Jun Heo
Fabricating Simple Wax Screen-Printing Paper-Based Analytical Devices To Demonstrate the Concept of Limiting Reagent in Acid–Base Reactions ~ Pithakpong Namwong, Purim Jarujamrus, Maliwan Amatatongchai, and Sanoe Chairam
ULg Spectra: An Interactive Software Tool To Improve Undergraduate Students’ Structural Analysis Skills ~ Armelinda Agnello, Cyril Carré, Roland Billen, Bernard Leyh, Edwin De Pauw, and Christian Damblon
Exploring Materials Science
Preparation of Octadecyltrichlorosilane Nanopatterns Using Particle Lithography: An Atomic Force Microscopy Laboratory ~ Zachary L. Highland, ChaMarra K. Saner, and Jayne C. Garno
Extended Hückel Calculations on Solids Using the Avogadro Molecular Editor and Visualizer ~ Patrick Avery, Herbert Ludowieg, Jochen Autschbach, and Eva Zurek
Engaging Teaching Approaches
The People Periodic Table: A Framework for Engaging Introductory Chemistry Students ~ Adam Hoffman and Mark Hennessy
Chemical Analysis of Household Oxygen-Based Powdered Bleach: An Engaging Approach to Teaching Sampling of Heterogeneous Materials and Addressing Statistics ~ Mauro S. F. Santos, Alexandre L. B. Baccaro, Guilherme L. Batista, Fernando S. Lopes, and Ivano G. R. Gutz
Introducing a Simple Equation To Express Oxidation States as an Alternative to Using Rules Associated with Words Alone ~ Piotr Minkiewicz, Małgorzata Darewicz, and Anna Iwaniak
Historical Perspectives
Celebrating the Golden Jubilee of the International Chemistry Olympiad: Back to Where It All Began ~ Fun Man Fung, Martin Putala, Petr Holzhauser, Ekasith Somsook, Cecilia Hernandez, and I-Jy Chang
Crime in the Classroom: Analysis Over 26 Years ~ David N. Harpp
Distilling the Archives: Lab-on-a-Chip and Microfluidic Devices
This issue include an open access article, Lab-on-a-Chip: Frontier Science in the Classroom, by Jan Jaap Wietsma, Jan T. van der Veen, Wilfred Buesink, Albert van den Berg, and Mathieu Odijk in which students experiment to discover the principles of microfluidics. In Fabricating Simple Wax Screen-Printing Paper-Based Analytical Devices To Demonstrate the Concept of Limiting Reagent in Acid–Base Reactions, Pithakpong Namwong, Purim Jarujamrus, Maliwan Amatatongchai, and Sanoe Chairam use paper as an inexpensive microfluidic device. Additional articles on microfluidics in past issues can been explored, such as:
Chemistry in Microfluidic Channels ~ Matthew C. Chia, Christina M. Sweeney, Teri W. Odom
Microfluidics for High School Chemistry Students ~ Melissa Hemling, John A. Crooks, Piercen M. Oliver, Katie Brenner, Jennifer Gilbertson, George C. Lisensky, and Douglas B. Weibel
Electrolysis of Water in the Secondary School Science Laboratory with Inexpensive Microfluidics ~ T. A. Davis, S. L. Athey, M. L. Vandevender, C. L. Crihfield, C. C. E. Kolanko, S. Shao, M. C. G. Ellington, J. K. Dicks, J. S. Carver, and L. A. Holland
A Student-Made Microfluidic Device for Electrophoretic Separation of Food Dyes ~ Saowapak Teerasong and Robert L. McClain
Using Paper-Based Diagnostics with High School Students To Model Forensic Investigation and Colorimetric Analysis ~ Rebekah R. Ravgiala, Stefi Weisburd, Raymond Sleeper, Andres Martinez, Dorota Rozkiewicz, George M. Whitesides, and Kathryn A. Hollar
Fabrication of a Paper-Based Microfluidic Device To Readily Determine Nitrite Ion Concentration by Simple Colorimetric Assay ~ Bo Wang, Zhiqiang Lin, Min Wang
A Simple Paper-Based Microfluidic Device for the Determination of the Total Amino Acid Content in a Tea Leaf Extract ~ Longfei Cai, Yunying Wu, Chunxiu Xu, and Zefeng Chen
Cost Effective Paper-Based Colorimetric Microfluidic Devices and Mobile Phone Camera Readers for the Classroom ~ Myra T. Koesdjojo, Sumate Pengpumkiat, Yuanyuan Wu, Anukul Boonloed, Daniel Huynh, Thomas P. Remcho, Vincent T. Remcho
Yes, You Can Have More!
With 95 volumes of the Journal of Chemical Education to examine, you will always find something useful—including the articles mentioned above, and many more, in the Journal of Chemical Education. Articles that are edited and published online ahead of print (ASAP—As Soon As Publishable) are also available.
Do you have something to share? Write it up for the Journal! For some advice on becoming an author, it’s always very helpful to read Erica Jacobsen’s Commentary. In addition, numerous author resources are available on JCE’s ACS Web site, including recently updated: Author Guidelines and Document Templates.
As I drive home from work every day in Houston, TX I am greeted by the entrancing voice of Dr. John Lienhard, now an Emeritus Professor of Mechanical Engineering and History at the University of Houston. His radio program, The Engines of our Ingenuity, has aired daily since 1988 and, as he says in his signature signoff, concerns itself with “the way inventive minds work.” The radio program broadly discusses various aspects of human invention, and I do mean broadly. Episodes touch on everything from engineering, physics, and chemistry to philosophy, literature, and the arts.
I have long been fascinated by the stories behind human discoveries and intellectual production. For every equation, every theory, every invention, every great work of literature, there are a multitude of personalities, rivalries, collaborations, and other tales of intrigue. Some are well known, such as the great Leibnitz-Newton debate over the calculus and its notation. Other characters are less well known. Take Johann Loschmidt, whose work helped lay the foundation for the Kinetic Molecular Theory but is often not remembered in textbooks. He was the first to approximate the size of a molecule and the number of molecules in a given volume of gas, but the famous constant to come from this work was named for Amadeo Avogadro. Loschmidt’s name was eventually given to the number density of particles in an ideal gas, an obscure an unused value, at least in most classrooms.
Last year, my students were particularly touched by the story of Harry Moseley, one of the most promising young scientists of the early twentieth century. At one point a student of Ernest Rutherford, he went on to discover that the charge of the atomic nucleus was unique to each element, assigning physical meaning to the atomic number for the first time. Driven by duty to his country, he enlisted in the British Army and was killed at Gallipoli in 1915 at the young age of 27. The author Isaac Asimov wrote that his, “may have been the most costly single death of the War to mankind generally.” My students had recently learned about the Battle of Gallipoli in their history course and were stunned by this additional tragic tale. One came in to class every day for a week and kept repeating, “Why did he go to the war? Imagine what he would have done!”
I love seeing the questions and emotions these stories elicited in my students. Despite my daily efforts to have my students draw conclusions from data and build their own models of matter from observation, the genuine humanity that is present in scientific inquiry sometimes eludes them when they are lost in the weeds of a school year. I am determined to help them see this beautiful side of what we study.
The first way I did this was in my earlier post on the Nature of Science, which is a good accompaniment to this one, as they both try to open students eyes to the broader picture of scientific inquiry, its history, philosophy, and cultural impact. The episode below, entitled “Only a Theory”, would make a good companion to the activity in that post.
The next way I am trying to do this is to incorporate Engines of Our Ingenuity episodes in to my classes. A few months ago, I learned that all episodes are available online and searchable. I began compiling a list of relevant episodes for my chemistry courses which I have included below, roughly sorted by topic. I plan to update this list on this post as I continue to add to it.
I currently do not have any structured activity that I have developed to go along with these radio episodes. I usually throw in an episode at the beginning or the end of a class to provide my students with a different avenue through which to engage with the content of the course. For example, after a detailed lesson on voltaic cells and potential difference in my AP Chemistry class, we concluded with “The Magic of Batteries” which provides an elegant and simple description of basic electrochemistry and allows the students to appreciate the wonder and beauty that accompanies the complexities and nuance of our study. Following our development of the Atomic Molecular theory, I shared with them “John Dalton’s Notation” which describes how revolutionary Dalton’s particulate drawings of atoms were in a community that did not fully accept the reality of atoms. My students giggled at Dalton’s love of lawn bowling, and his description as a reclusive, awkward man.
Perhaps we discuss them for a few moments, but I have not developed a larger activity or project yet. Maybe one need not be developed, maybe listening and allowing our minds to enjoy and wonder are enough. Sometimes I don’t think we let our students do that enough.
I hope you take the time to listen to and enjoy these episodes I’ve listed below, and the thousands of others catalogued on the website. I am very curious to hear how you see something like this fitting in to your chemistry class. Do you have any other ideas for how to incorporate them, perhaps in a way that students can more deeply engage with them? I very much look forward to the conversation!
Sign up for the Podcast here.
The searchable database of all episodes is here.
The Atomic Molecular Theory
John Dalton’s Notation: http://www.uh.edu/engines/epi1411.htm
Hard Atoms in the Essence of Fire: http://www.uh.edu/engines/CD-RainSteamSpeed/track5.html
Atomic Structure
Modeling the Atom: http://www.uh.edu/engines/epi2237.htm
Johann Josef Loschmidt: http://www.uh.edu/engines/epi1858.htm
Robert Millikan: http://www.uh.edu/engines/epi2019.htm
HGJ Moseley: http://www.uh.edu/engines/epi717.htm
Thermodynamics
Temperature: http://www.uh.edu/engines/epi1764.htm
A Thermodynamics Class: http://www.uh.edu/engines/epi732.htm
Louis de Broglie: http://www.uh.edu/engines/epi2270.htm
Wrong Hill to Die Upon: http://www.uh.edu/engines/epi946.htm
The Elements
Naming the Chemical Elements: http://www.uh.edu/engines/epi1235.htm
Oxygen: http://www.uh.edu/engines/epi86.htm
Hydrogen: http://www.uh.edu/engines/epi1604.htm
Electrochemistry/Oxidation-Reduction
The Magic of Batteries: http://www.uh.edu/engines/epi2893.htm
The Baghdad Batteries: http://www.uh.edu/engines/epi1972.htm
The Nature of Science and Science Education
Only a Theory: http://www.uh.edu/engines/epi1531.htm
Absolutism: http://www.uh.edu/engines/epi2132.htm
Miscellaneous
The Death of Lavoisier: http://www.uh.edu/engines/epi728.htm
Marie Lavoisier: http://www.uh.edu/engines/epi1673.htm
A Tale of Three Scientists: http://www.uh.edu/engines/epi704.htm
The Second Industrial Revolution: http://www.uh.edu/engines/epi2694.htm
Mass, Length, and Time: http://www.uh.edu/engines/epi1860.htm
In an effort to align my lessons with the Next Generation Science Standards (NGSS), I have tried to take the content I have traditionally taught, and shift the design to focus on student engagement with the science and engineering practices outlined in the standards. For the topic of heat transfer I re-packaged the ice melting blocks discrepant event as a NGSS investigative phenomena.
One way to align this lesson with a pedagogy style supported by NGSS is to have students observe the phenomenon and then generate questions about what they saw. This engages students asking questions, one of the science and engineering practices. The question formulation technique (QFT) that I discussed on ChemEd X last month, can be used to develop student questions. Students were first asked to make observations about the blocks prior to the demonstration. Many recorded color and shape as well as mass and temperature differences between the blocks. All students recorded that one block “felt colder” in their observations. Students also noted when ice cubes were placed on both blocks, the ice melted faster on the one that “felt colder.”
Students generated questions on the phenomena individually and then as a group of four students. Each group came up with a minimum of ten questions. The students then changed their closed-ended questions to ones that were open-ended and picked the groups’ top three questions they had about the phenomena. Each class then developed a list of the top burning questions they wanted to explore. The questions were recorded on white paper and placed on a white board in the front of the room. The following is a sample question set generated by one of my classes (Figure 1).
Figure 1 - Example of a list of questions developed by one of my classes.
Following the question formulation technique protocol, students were asked to vote on the question they were most curious about from the class list. Most classes picked a question related to why the ice melted faster on one block.
Next, students were instructed to use another science and engineering practice, developing and using models to the answer to the class question. Students were given about five minutes to create/draw an individual model and then compare and create a group model on white boards. This was followed by a gallery walk of the models where students took notes on how they should adjust their model or leave it if they felt their model was most adequate. Then, a spokesperson from each group explained their model to the class.
After the last group presented their initial models, the class was asked to provide one piece of positive and negative feedback for each model. One of the benefits of this type of exercise is the shift in class culture as students openly share through positive feedback and constructive criticism how to improve each other’s models. One group chose to create an analogy of the metal block that melted the ice faster to that of a metal slide in a park (Figure 2).
Figure 2 -One group chose to create an analogy of the metal block that melted the ice faster to that of a metal slide in a park.
I was amazed at the creativity and explanation of how the slide feels hot on a summer night but freezing on a winter day. The most common type of model drawn (Figure 3) shows both blocks with particulate representations but is lacking clarity on the heat transfer or thermal conductivity, which is typical for an introduction to the thermochemistry unit.
Figure 3 - The most common group model.
Every single class had groups ask a question such as: “What would happen to the rate of ice melting if the blocks were at the same initial temperature.” The second day after the students’ models were created, I had students record several pieces of data: the temperature of the two blocks, the student desk top, and the metal legs of the desk using an infrared thermometer. This was to show the students the blocks were at the same temperature - room temperature. The students were amazed by this and were then given the chance to revise their models.
The point of this is the students’ models can constantly be modified as new information is learned over the course of the unit. This is difficult for me as an educator since I feel I should never allow students to leave with incorrect information. However, as students learn new information, they are more interested in trying to find an answer to the chemistry behind the novel phenomenon in the lessons that follow. I adapted a handout from the Right Question Institute for this activity. It can be found in the supporting information below.
This activity was a beautiful way to capture students’ prior knowledge about heat transfer. In the past, I have done pre-assessments such as anticipation guides to gauge students’ knowledge. But, never have so many misconceptions been revealed as they have with this QFT activity. Most of the time students mentioned that something “felt cold” due to something in the cold substance moving to the hotter substance, a misconception to heat movement from a hotter to colder temperature. My students learned about heating and cooling curves in middle school and know both solid and liquid phases are present at the melting point. However, to my surprise many of their models did not incorporate both phases at the particulate level during melting.
When groups challenged each other, some students elicited an alternate conception that the solid phase is present for the first half of melting and then it transforms to liquid only for the second half so both are present, but not simultaneouslyThis was how they justified graphs they had seen where both phases were present at the melting point! Many groups mentioned surface area/texture of the blocks as an explanation for why the ice melted faster and thought the material on one of the “warmer” block kept the ice cubes glued together and prevented melting. One group took it one step further explaining that the “warmer block” contained a hydrogen bonding blocker type substance that functions similar to the way inhibitors block enzymes. This explained why the ice didn’t melt as fast. Two groups in separate classes felt that heat flows from one object to another through tiny holes through an invisible mesh at the interface of each block, an interesting alternate conception I have never thought of. One group in each class mentioned conductivity as the answer to the phenomena, the correct concept, and some even mentioned the idea of freely moving electrons but had difficulty expressing the chemistry in a model. This is exactly what is desired, because the model will be adapted and modified over the course of the unit as more information is discovered.
Lastly, I would encourage teachers to model with their students. I have a student who just entered my class this past month and drew his model as a block of ice with wavy lines next to the block to represent ice that had melted into water. This student is extremely bright, but his previous school did not use Modeling InstructionTM. It was encouraging to hear the other students explain he was drawing the “macroscopic” level when he needed to draw on the “microscopic level” and this could be done with a zoom bubble! One takeaway from this student is despite the fact that he learned to draw a water molecule perfectly in one context at his previous school, he could not make the connection to the particulate level in this activity. This is a great example of how we, as teachers, need to constantly reinforce the idea that matter is made up of particles. Thus, if we do not reinforced this idea over and over, students may continue to think on a macroscopic level and visualize substances like water as wavy lines. They may miss the opportunity to see the particulate story of chemistry and the interconnections between topics within the course.
Editor's Note: Read Stephanie's previous post introducing the ChemEd X community to QFT (question formulation technique).
heat transfer, heat capacity, phase change
two class periods
Obtain at least two ice melting metal blocks and an infrared thermometer.
Quoted from the Amazon.com page for the ice melting blocks: "Place an ice cube on each of these two identical looking black blocks at room temperature. One ice cube instantly begins to melt and is totally gone in about 90 seconds. The other ice cube shows no evidence of melting whatsoever. Great for showing the difference in heat conductivity in different materials. Set of two blocks.?
Refer to the student directions in the QFT Student document.
Refer to the student directions in the QFT Student document.
Prepare ice to be used in the demonstration.
The student handout is adapted from the Right Question Institute.
I love the periodic table. Proclaiming this feels appropriate for Valentine’s Day week, with its modern-day opportunity to declare one’s love and affection (although typically not for a chemistry tool, no matter how elegant and engaging). The curriculum in the K–6 science classrooms where I volunteer had a periodic table focus this week, so part of my method of familiarizing them with the table itself was to share an “Elemental Valentine’s Day Advice” puzzle gleaned from the February 2018 issue of Chem13 News. I like fun, short activities like these where students get to know element names and symbols, along with their atomic numbers, in order to reveal words. There have been many throughout the years in the Journal of Chemical Education as well.
But, of course, there’s much more to the table than that. The February 2018 issue of the JCE offers one way to help students understand the table more in depth, particularly its repeating trends and how one can use the information the table contains. Hoffman and Hennessy discuss the method they used with high school and college chemistry students in The People Periodic Table: A Framework for Engaging Introductory Chemistry Students (available to JCE subscribers).
The instructor arranges seating before students enter the room, limiting where students may choose to sit. As students select their seats, they are not aware of their literally elemental role in the arrangement (see figure 1).
Figure 1 – Reprinted with permission from The People Periodic Table: A Framework for Engaging Introductory Chemistry Students, Hoffman and Hennessy. Journal of Chemical Education, 95 (2), 281–285. Copyright 2018 American Chemical Society.
Their place in the People Periodic Table is soon revealed, when students are assigned to identify their personal element. From that point, the authors’ classes “engaged in predictions regarding the … periodic properties of atomic size, electronegativity, ionization energy, electron affinity, and metallic character.” The classroom-sized scale of the table and visual aspect of the questions/answers (e.g., point in the direction of the person with the largest ionization in their period) help to illustrate the idea of a periodic trend.
The article has online supporting information that outlines the activity and questions to use. Although this formula can get one started, it is not a formulaic activity—instructors should be ready for teachable moments to crop up, in the authors’ experience. When discrepancies in student answers arise, they suggest using the opportunity for the student elements themselves to discuss with their surrounding elements which is correct and why. The supporting information also has suggestions for different seating arrangements for groups from 8 students to more than 45.
Can’t get enough of the periodic table? Check in with a recent XChange post that generated a lot of discussion about memorizing element names and symbols. Where do you fall on the memorizing (or not) spectrum? See Jordan Smith’s post I Have My Students Learn All of the Elements...6 Strategies I Use.
More from the February 2018 Issue
Mary Saecker’s post JCE 95.02 February 2018 Issue Highlights summarizes the issue for you. The glowing cover caught my eye—she briefly describes how the images were obtained, along with a link to the related demonstration.
Do you have a past JCE activity or article on the periodic table that you love? Please share! Start by submitting a contribution form, explaining you’d like to contribute to the Especially JCE column. Then, put your thoughts together in a blog post. Questions? Contact us using the ChemEd X contact form.
Something about Ben Mecheam's Blog, "Using Evidence to Determine the Correct Chemical Equation: a Stoichiometric Investigation" really got my interest. First, I was interested because my students struggle with stoichiometry and I am always looking for new ideas to approach it. Second, I have never seen it done this way and had not heard of the book he was using. Also, I thought the approach was new and novel. I was able to get a copy of "Argument Driven Chemistry" and here I will share what I discovered.
There are two aspects about this book that stand out. First, there is the content. I quickly looked at the thirty plus activities in the table of contents. I found activities that could be used for a general chemistry class, advanced and even AP. The materials were well organized and each topic that I have examined so far provides more than enough information for the instructor. Also, it was written and reviewed by practitioners.
The second and most impressive part of the book is the pedagogy. It is not just the topics but how they are presented. Argument Driven Inquiry takes a different approach than some other inquiry programs. Here is a general framework of how students and teachers approach a problem in science in a Argument Driven Inquiry (ADI) classroom. (By the way, the website Argument Driven Inquiry provides ample support, ideas and graphics if you want to try it in your classroom...I would encourage you to give it a look.) Here are the general steps for a lab. These are also similar to the steps I tried with my students the first time I attempted this method. The first lab activity we tried was about moles. Students were given a container that contained one of six known substances. The container had a letter and the number of moles written on the container. They had to figure out which of the six compounds they might have in the container.
1. Identify the task and develop a guiding question. A problem was presented. The class as a whole agreed on a task and / or guiding question.
2. Design a method and collect data. I had individual lab groups agree on the method and data collection. I did not tell them if they were correct or not. I simply gave them the green light to try and made sure they were being safe.
3. Develop an initial argument. Each group stated their "Question", "Claim", "Evidence" and "Justification" on a whiteboard once they collected and processed the data. See figure 1.
Figure 1 - Students present their question, claim, evidence and justification on whiteboards.
4. Argument Session. Students now go around and look at other student's ideas. I had each group do an "elevator" pitch. They had about 30 seconds to a minute to sell their ideas to other students.
5. and 6. Reflective discussion and Report. These two meshed together. Students could discuss, keep or change any ideas as groups and individuals. Next, as individuals, they wrote a one page report that was the same format as the whiteboard. They could keep or change any ideas they received from their group or the class. I had them submit the report through "Google Classroom" electronically (see figure 2).
7. Double blind group peer review. Every name on each report was deleted. A code was put in place of the name and three copies were printed. Students received mutliple copies. They were asked to read each one and make comments on the paper. Argument driven inquiry provides rubrics. Essentially, I asked students that if they were reading this report, would it make sense to them? If not, why not? Students then received multiple copies of their rough draft and the critiques. They could decide what information to use in their final report.
8. Submission of final report. Students then submitted their final report.
Overall, I was extremely please with this process for several reasons. In guided inquiry activities, I constantly find myself having to provided different types and amount of guidance based on the students. Students determine the guidance they need from each other in ADI. The vast majority of students not only found the correct unknown but did a really good job of explaining how they came to their conclusion. Many individuals solved for the unknown in ways that I would not have but they still found the correct answer and showed their work. I was totally o.k. with their arguments and answers. Finally, and probably the most important reason I will start using this method more often is that some of my students that I have struggled to engage, we indeed highly engaged and motivated in this process and they did a great job. This alone is enough to sell me on this book. I can highly recommend it.
Figure 2 - Sample student reports.
ADI in Chemistry
Argument Driven Inquiry in Chemistry is published by NSTA Press. NSTA members receive a discount on these books when ordered through the NSTA website. There is also an e-book option.
ChemEdX February 2018 Update
By now, a lot of you have been able to watch the Winter Olympics. If you are like me, you have been able to draw similarities and relevance to what you are teaching in the classroom.
For example, my Chemistry 1 semester classes recently reviewed the idea of accuracy and precision. Curling is a wonderful example for discussing those concepts. Perhaps you have covered significant figures and limits of accuracy by discussing the difference in timing among the different sports (recording to the hundredths place vs. the thousandths place). Maybe you teach physics - the physics of curling (momentum, inertia, etc) or ski jump (trajectory, velocity) would be relevant.
You might be interested in reading Doug Ragan's post about Significant Digits, Pool Tolerances, and Ties in Swimming.
What other lessons come to mind from the Winter Olympics? How might these lessons relate to NGSS? Comment below!
The unit of acids and bases is difficult for most students in Advanced Placement Chemistry. The variety of various calculations can be overwhelming. I decided it was time to make the pH calculations more exciting. After completing notes and examples on each type of solution throughout the unit, the students in my AP class were given a handout to organize the calculations. The students completed the "Student Notes for solving pH problems" (download a copy of the document below) and reported out their answers. After this quick review, my students were each assigned a specific solution. I had made a list of 10 solutions that repeat depending on how many students I have in class (I have 32 this year). The activity is easier when there are multiple students with the same solution. It makes finding a “date” faster. I made the quantities easy enough that students can quickly calculate and compare because the objective of the lesson was to recall the method to calculate the pH quickly, not to stump the students. Each student was asked to determine their individual pH to complete their personal “Solution Biography.” Then it was time to speed date! For each date, the students needed to find a specific match and determine their combined pH value.
My favorite quote of the day was “I can’t leave my match, we made a perfect buffer and we resist change!”
For date #1, students were asked to find a student holding a match where both solutions were of the same strength and classification (weak acid matching another weak acid or strong base matching another strong base). They were asked to calculate their combined pH value by calculating their combined moles, combined volume, combined Molarity and finally combined pH. We reported out a summary of what happened to the pH (when two of the same concentrations were mixed, the pH remained the same but when two different concentrations were mixed, the pH changed).
For date #2, students were asked to find another student with a similar solution of a different strength (for example a weak acid had to find a strong acid). They had to realize that the stronger solution determined the pH, but only after being diluted by the weak solution.
Date #3 was tricky! The students had to find a partner to make a buffer solution with. Some students had a difficult time finding dates, so after the initial dates were found we had a pool of students in the center of the room to help everyone find a match. I went around and checked the solutions to confirm their match. The biggest take away was that the students realized they needed to pair up to achieve a solution in which the weak solution contains more moles than the strong solution.
Our last date required students to find a match to create a salt. They had to estimate the final pH, indicating whether the solution would result in a neutral, acidic, or basic salt. The students had to find a match with equivalent moles. After all students were matched, each pair read their individual solutions and in unison reported out their salt type and estimated pH (7, higher than 7, or lower than 7). The trickiest examples were matches in which both solutions contained weak electrolytes (in which case the students had to compare K values).
You can make modifications to the activity, but keep in mind when you are modifying the solutions list that the trickier the numbers are, the more difficult it will be for students to find a match quickly. It is important to make sure everyone will indeed have a match for each date. For uneven number of students, I had two struggling learners pair up as one solution. You may also choose to differentiate the students by assigning weak solutions to your best performers and strong solutions to your struggling learners. We completed the activity in 50 minutes. I observed smiling, excited students eager to find matches. After class I asked a few students what they thought of the activity. All five students said it was more fun than normal problem sets and they would love to play again. Another student remarked that she “understands dilutions and strength much better now.” And my favorite quote of the day was “I can’t leave my match, we made a perfect buffer and we resist change!”
acid base, neutralization, pH, concentration, molarity,
One class period
Pre-made sets of cards containing one of each of the following solutions. Repeat as necessary to accomodate for the number of students.
List of Solutions Used
10mL 1.0M HA Ka=2.0x10-7
10mL 1.0M HCl
10mL 1.0M NH3 Kb=1.8x10-5
10mL 1.0M NaOH
20mL 1.0M HA Ka=2.0x10-7
20mL 1.0M HCl
20mL 1.0M NH3 Kb=1.8x10-5
20mL 1.0M NaOH
40mL 1.0M HA Ka=2.0x10-7
40mL 1.0M NH3 Kb=1.8x10-5
Assign Calculating for pH review worksheet to be completed at the beginning of class.
Distribute one card per student identifying them as a specific acid or a base and their concentration. Students will complete a series of four "dates".
Create the cards. You can laminate them and reuse.
I created the activity for my students.
In a previous post, I learned that a Scrub Daddy sponge is mainly comprised of a polymer called polycaprolactone.1 I have continued to gather information on polycaprolactone and also to experiment with Scrub Daddy sponges. For example, I learned that the glass transition temperature of polycaprolactone is 213 K (-60oC or -76oF).2 The glass transition temperature,Tg, is the temperature above which a polymer transforms from a brittle, glassy state to a flexible, elastic state. Thus, it would make sense if a Scrub Daddy sponge could be cooled below its Tg when immersed in liquid nitrogen, which is at 77 K (-196oC or -321oF) – well below Tg for polycaprolactone. I decided to cool a Scrub Daddy in liquid nitrogen and subsequently hit it with a hammer to find out:
The Scrub Daddy certainly displayed brittle, glassy characteristics when cooled to 77K! After doing this experiment, I noticed that the temperature of dry ice, 196 K (-78.5oC or -109oF), is below Tg for polycaprolactone. This made me wonder if a Scrub Daddy would shatter when struck with a hammer after being cooled using dry ice. If this experiment worked, I figured it might give experimenters who have access to dry ice a cool way (pun intended) to shatter items without requiring the use of liquid nitrogen, which is often difficult to obtain. In the video below, you can see what I found out:
As you can see, the Scrub Daddy did shatter when struck with a hammer after being cooled in dry ice! So if you don’t have access to liquid nitrogen, you can still demonstrate the shattering of a cooled item using a Scrub Daddy, dry ice, and a hammer.3
Let me know if you and your students try some experiments with the Scrub Daddy sponge. Also, I would be interested to hear if anyone learns of any other materials that can easily be shattered by striking with a hammer after cooling in dry ice.
Happy experimenting!
1. https://www.chemedx.org/blog/scrub-daddy-science
2. Progress in Polymer Science, 2010, 35, 1217-1256.
3. Notice that the Scrub Daddy was cooled in dry ice only, and not a mixture of dry ice and alcohol (or acetone). Striking the Scrub Daddy after cooling in such mixtures would likely cause organic solvents to be splattered about, causing an unnecessary hazard.
